Radio shielding



Feb 4, 1941 M.A F. PETERS Erm. 2,230,261

mno SHIELDNG ATTORNEY.

iw M. F. PETERS ETA. 2,230,26l

RADIO sHIELDme 4Filed March 16, 1958 2 Sheets-Sheet 2 FG-EE FIG. M

FIG. 9 41 4@ l2@ INVENTORS. 21E/l- '5 me...

ATTORNEY.

Patented Feb. 4, 1941 zamen PATENT OFFICE- RADIO SHIELDIN G i 'Melvme F. Peters, Beltsville, Ma., ma n. nan-yi 4 Stone, Bound Brook, N. J., assignors to Tlteilex Metal Hose Co., a corporation of New Jersey Application March 16, 1938, Serial No.' 196,284

15 Claims.

This invention relates to the provision of means for shielding apparatus from which radio waves might'emanate to possibly interfere with the operation of radio communication apparatus, such that radio waves from the mst-mentioned apparatus may be prevented from such interference to amr deleterious or undesired extent.

Such interference is particularly liable to occur in aeroplanes where the operation of the ignition system or systems of the internal combustion engine or engines ordinarily interferes to a serious extent with the radio communication apparatus on the plane especially as from the circumstances of the case the engine and the radio communication apparatus-mustbe in relatively close proximity.

I'he main object of the invention is to .provide improved radio shielding means which shall be simple in construction and eihcient in operation.

- In providing radio shielding heretofore the shielded parts have been so enclosed as to seriously interfere with the dissipation of heat from the parts and it has been aY matter of extreme concern vto avoid over-heating of the parts.

proved radio shielding means which shall permit ready dissipation of heat from the shielded parts whereby danger of over-heating is easily avoided.

In connection with the radio shielding of internal combustion engines it has been customary to shield the conductor, magnetos and spark plugs of the ignition system by placing shielding conduits about the conductors and shielding housings about the magnetos and spark-plugs. If the engine, including the ignition .system, is enclosed within the shield, the desired radio shielding may be accomplished but the necessary ventilation, to keep ldown the heat of the engine parts, will be interfered with.

It is a further object of the invention to provide a radio shield about some or all of the en` gine parts While permitting ventilation of the 4;, parts'. i A

The engine of an aeroplane is usually surrounded by a metal cowling through which the air is forced rearwardly about the engine, cool- Y ing it, by the forwardly located propeller for the i aeroplane.

It is a further object of this invention to utilize the covvlingV as a part of the radio shield about the engine, and it is arfurth'er object to complete the shield without unduly interfering with 5-'1 the ilcw of air impelled backwardly by the pro- It is an object of this invention .to provide impeller through the cowling and about the en l gine parts.

It is a further Aobject of the invention, in accomplishing some or all of the foregoing objects, to make at least a part of the radio shield fo- 5 raminous, and by foraminous is meant having a collection of openings whereby air is permitted to pass while the radio waves are interrupted whether the foraminous part is a meshed screen, formed of wires or slats, or is formed by slots 10 or wires (without cross slats or wires) with openings `between them. v

A further object of the invention, if one, foraminous part of a shield shall not provide the desired interception of .radio waves, is to provide l5 a plurality of such parts, one outside the other vwhereby'the desired shielding will be secured.

A further object of the invention is to effect the desired radio shielding by placing a shield about certain of the parts and employing an electric current nlter or filters for preventing undulyA disturbing currents from passing outside the shield.

A further object of the invention is to so position the slats or wires in the foraminated part of the radio shield with relation to the radio communic'ation apparatus that interference with the communication apparatus may be reduced or prevented. Y

A further object of the invention is to provide the desired radio `shielding without increasing the electrical capacity of the shielded parts to an extent as was the case in former radio shielding.

In radio shielding an ignition system for an internal combustion engine, the parts were custornarily surrounded by metal shields in close association with the shielded parts, whereby the electrical capacity was very considerably increased. Such increase in capacity caused less efficient operation and' required a larger powerY 40 output (and so larger and heavier apparatus) of vthe source of'ignition current and other parts.

The present invention provides means for accomplishing the desired radio shielding without s? the necessity of closely associating the shield with the electrical parts shielded whereby the electrical capacity is reduced from what it formerly was with corresponding advantages as indicated.

Other and ancillary objects of the invention will appear hereinafter. f

In the accompanying drawings which illustrate f the invention:

Fig. 1 is a side elevation, partly in longitudinal section, of a radialinternal combustion engine i 2 s,aso,as1

such as is ordinarily used on aeroplanes equipped with the improved radio shielding means;

Fig. 2 is a similar view of a radial internal combustion engine with a modiiled form of radio 5 shielding means;A

Fig. 3 is a sectional view on the line I -I ofI `Fig. 2, partly broken away, showing the relation of the meshes of a shield comprising a double screem l0 Fig. 4 is a front elevation of `the screen' as shown in'Fig. 3;-

'Fig.'5 is aside elevation, partly in longitudinal "'I" Fig. 'I is a perspective view of the form of screenassedinFig.-6:

Fig. 8 is a side elevation, partly in longitudinal section, of a radial internal combustion engine. having 'a further form-of radio shield to- 25 gether with an antennae for .a radio receiving Set;

Fig. 9 is an elevation, partly broken'away.

of the shielded engine of Fig.v8, viewed from theright hand side of Fig. 8. with the propeller 80" removed;

Fig. 10 is a perspective view of the form of radio shield at the front of the engine as shown in Figs. 8 and 9; 'i

Fig. 1l is a side elevation. partly in section. of an internal combustion engine having a number of cylinders in one or more straight lines and equipped withI a radio shield in accordance with the present invention:

, Fig. 12 is a fragmentary view showing a modiiied manner of relating the current filter of Fig. 1l to the radio shielding screens;

Fig. 13 is a view similar to Fig. ll, but showing the radio shield about the spark plugs asconsisting of a single screen; and A Fig. 14 is a cross section, on an enlarged scale of a modied form of slat.

Referring to the drawings and first to Fig. l, the radial aeroplane 'engine shown thereincomprises the crank case I having the cylinders 2 extending' radially therefrom. The cylinders are provided in the usual way with sparks plugs l which are supplied with ignition current from the magnetos l. The engine shaft 5 has the propeller 6 xed thereon and circumferentially surrounding the engine is the metal cowling 1. In the usual operation of the aeroplane' the air thrown backward by the propeller passes through.

the cowling and about the engine thereby cooll ing the parts.. To still permit this current of 50 air through the cowling and about the engine meshed, metal, wire screen l is secured to the mrwardjedge of the cowling at l and ha'. its rear edge I0 sec to the engine. This screen extends entirely across the space between the cowling and the engine'at all points about the engine and cowling.` Also a metal wire mesh screen 68 extends from the edge I0 of the screen l to the engine crank case I entirely about the circumference and is in gobd and iirm electrical 70 connection with the screen -l and the crank case I. To.permit the air to pass backwardly through the cowling there is a similar metal wire mesh screen IIv secured at its edges to the c0wling1 and extending across the entire space 7s between the walls of the cowling. The meshed .Dl'iis a8 also referred to.

screen 8 should have a .thoroughly grounded connection with the cowling at 9 and also with the metal of the engine cylinders at I0. Also the edge of the screen Il should have a thoroughly good grounded electrical connection with the cowling 1.

The ignition system-of the engine is entirely radio shielded because housed in a completely enclosing housing comprising' the metal, such as for instance the cowling and metal engine parts l0 and the metal screensreferred to. As is well known the sheet metal and engine parts, without openings, will operate as a radio shie1d,and it has been discovered that radio shielding may bel accomplished by meshed screens as'described l5 while permitting the ventilation of the engine The size of the screen mesh `will depend upon the location of the screen with relation to the parts to be shielded. This i can be readily ascertained by a few trials with 20 screens of different sized meshes in any given locationy the emciency of the screen being tested by well known instruments in well known ways to ascertain the presence of undesirable radiationsputside the screen. While, as stated, the 25 size of the screen mesh will vary according to conditions, good shielding has been obtained underdiiferent conditions with screens having a width of mesh of from one-twentieth to onequarter ofv the distance of the/,screen from the 30 antenna..that is the part from which the radio emanations are to be, intere pted.

It may be that the m es of a. single foraminous radio screen may ybetoo large to intercept the radio emanations to the desired degree. 35

reasons. Under such circumstances the desired radio shielding may be accomplished by placing I a plurality otforaminous screens one outside the 40 others and preferably spaced apart. Thus in Fig. 2 the aeroplane] engine which, like that of Fig. 1, has the crank case I2, the radial cylinders I3, the magnetos Il and the Vspark plugs I8, which engine is surrounded by the 45 sheet metal cowling I8. vThe engine has the propeller I1 fixed upon the engine shaft Il forwardly of the engine. 'I'he radio shielding in Fig. 2, like in Fig. `l, is accomplishing by enclosing the ignition system of the engine with 5 the cowling and meshed metal wire screens at the forward (toward the propeller) portion of the cowling, and a similar screen rearwardly of the engine.

In the case of the apparatus of Fig.' 2, how- '55 ever. the desired radio shielding may not be accomplished by a single foraminous screen and therefore -a plurality of screens, one outside the other and spaced apart, is shown at'the forward end of the cowling and also `rearwardly of 60 the engine. Thus referring to Fig. 2, there is at the forward portion of the cowling a meshed metal wire screen I! which surrounds the crank 'case.andatitsinneredgeisinnrmandgood while its inner edge is in good and firm electrim' connection with the crank case sf. zo. Each of the screens Il and 22 extends across the entire space from the crank case to the cowling at all points about the circumference of the cowling and the crank case.

At the rear of the engine is placed a metal wire meshed screen 24 whichrextends entirely across the space between the walls of the cowling at all points and has a nrm and good electrical connection with the cowling at its circumferential edge 28.

In order to procure a greater interception of the radio waves a metal wire meshed screen 24 is spaced from and placed outside of the screen 24, which also extends across the space between the walls of the cowling at all points and is secured in good and firm electrical connection with the cowling at its circumferential edge 21.

I-t will now be seen "that the engine ignition is entirely enclosed within a radio shield comprising the metal parts of the engine. thecowling and the metal wire meshed screens at the 'front and rear of the engine. It will further -be seen that if, for any reason, either of the screens I! or 22 is of such large mesh as to not in itself provide suflicient radio shielding, the presence of the other lscreen increases the radio shielding If two screens, one outside the other, should not be s'uillcient, any desired number of screens might be placed one outside the other until the desired radio shielding elect was secured. Also with regard to the rearward meshed screens 24 and 26, lthey supplement each other in suppressing the undesired radio waves so that if for any reason one of the screens should be insumcient to constitute a radio shield to the desired extent, the other screen may furnish sunlcient additional shield` ing. In some instances where desirable agreater'number than two screens might be provided. one outside the other.

I'he construction and relationship of the screens 24 and 28 is shown in .the fragmentary views of Fig. 3 and Fig. 4, it being observed (see particularly Fig. 4) that the meshes in the two.

screens are staggered with relation toeach other, although this is not absolutely necessary.

Referring now to Figs. 5, 6 and 1, the aeroplane engine similar to Ithat of Figs. 1 and 2 has the c rank case 28 from which project radial cylinders 29 having the usual spark plugs supplied with current by the magnetos 3l, such engine having the usual metal cowling 22 enclosing the engine circumferentially. The propeller 33 is ilxed upon the engine shaft 34.

In order to complete the radio shield about the engine ignition -there is placed at the forward end of the cowling a metal foraminous screen Il which, instead of being formed by -wires as in the screens of Figs. 1 and 2,is formed by vsets of iiat slats and 21 crossing each other to' formA openings surrounded by the fiat slats, the greater dimension of the cross section of each `"of the slats extending in a forward and back direction substantially in line with the direction ofthe lbackward flowing air from the,A propeller. By

thus elongating the mesh forming members by providing slats instead of wires, with the elon- Y gated dimensions of the cross section rof the slats extending in a forward and back direction as described, the air resistance presented by the i'oraminated screen is greatly reduced. The

engine, the screen' extending across the entire space between the crank Vcase and the cowling at all points circumferentially of the cowling and* the crank case. V

Rearwardly of the engine thev radio shield may be completed by means of the wire meshed screen 28 which extends entirely across the space between thewalls of thecowling and is securd in good electrical connection with the cowling at l! at its circumferential edge. In place of the wire formed foraminous screen 38, this screen could also be formed by slats the same as the screen 35 with the greater dimension of cross section of the slats extending forwardly and rearwardly a's explained.

By providing the screen with the slats extending at right angles to each other as described, the screen will operate efdciently as aradio shield whatever may be the relationship of the antenna of theradio communication system to the position of the slats. 20

It` has been found, however, that a suitable radio shield may be provided if a series of substantially parallel members as slats (without cross members) is employed which are substantially parallel to the antenna of Vthe radio communication system which is to be shielded against interference.

Thus referring to Figs. 8, .9 and 10, the aeroplane engine, comprising the crank case 40 from which radially extend the cylinders 4| having 39 the usual spark plugs 42 supplied with current by the magnetos 43, the propeller 44 being mounted/upon the engine shaft 45, the engine being substantially the same asy that of Figs. 1, 2 :jf and 5, is circumferentially surrounded by the metal cowling 46 and the space between the cowling and thecrank case of the engine is occupied by the spaced fiat metal slats "which are each in' good electrical connection with the vcowling and with the crank case. It will be seen that these slats have their longer cross sectional dimension extending from front to rear as already referred to as reducing'the air resistance, and these flat slats 41 are substantially parallel to each other and' substantially parallel tothe 45 tenna 48, an eillcient and satisfactory shielding 50 is obtained.

Rearwardly of. the engine is a metal wire meshed screen 49 extending entirely across the space between the walls of the cowling and having good electrical connection about its circumference with the cowling at 50. In place of the radio Vscreen 49 -at the rear of the engine a set of parallel slats like 41 parallel with the antenna might be substituted to form the radio shield at the rear as well as at the front of the engine.

'I'he slats forming theslatted screens of Figs. 5 to 10, instead of being rectangular in cross section as in those figures, may each have a. different shape of cross section calculated-to'reduce the 65 air resistance or for other purposes, as for instance the slat cross section may be of a shape as shown in Fig. 14, the forward 'end' (at right `in Fig. 14) being broader and the section tapering rearwardly to a much narrower width at the 7o rear end (left in Fig. 14) this construction of slat gives a very low air resistance. j

v In Fig; 13 is' shown a manner'of application of the foraminous screen as completing a radio shield about the ignition'of an engine having 75 one or more straight rows of engine cylinders as is the practice in connection with automobiles. In the figure referred to the cylinders in the engine block 5I have the usual spark plugs 52 supplied with current through the distributor 53 and the usual spark coil 54 supplied with current through the conductor 55 in which is the dash boardv switch 56j. The source of ignition current is the battery 51 having one terminal connected with the switch 59 and the other terminal concurrent illter 59 is pnovided, such lter may "be as described in our application Serial No. 168,810, illed October 13, 1937, the exterior of such iiiter being mounted on the engine block by being secured in good and firm electrical connection with the screen 59.

4It will now be seen that any radio disturbanceby the ignition system :of the engine will be shielded against by reason of the factlthat the I ignition subject to disturbing variations is entirely enclosed in a Aradio shield, such radio shield being the metal ofthe engine blo'ckand the meshed screen 59, any disturbing variations of. current .in the ignition circuit 4being prevented from passing outside by means of the filter. If the engine is sufhciently cooled as by a suiilcient water jacket, so that Vventilation through the screen'59 is not required, an imperforate sheet metal radio shield may be used in place of the screen 59, the filter 59 preventing thepassage of disturbing variations to the outside of the shield.

In Fig. 1l is shown an arrangement similar to Fig. 13 for shielding the engine ignition except' that instead of one meshed screen enclosing the ignition -there are two meshed screens 9| and 92, one outside of the other and spaced from V"each other to provide satisfactory radio shielding in case'the meshes of one screen should be so large for permitting the desired ventilation or for other reasons, as not to completely eifect the desired radio shielding. The meshes of these two screens 9i and are to be staggered with re lation to each other as shown in Fig, 4. for the mostelcient operation, and both of these screens 5| and 92 should be well grounded by securing their edges in firm and good electrical connecv tion with the engine block. The current for the ignition system may be supplied by thelusual engine driven generator I9.' which is enclosed so as tobe radio shielded by the metal wire meshed screen M. Current is supplied from the generator by a conductor 95 passing through a current filter Il as it passes out from the shield Il and through anltertlasitpassesintothesparkcoil through the shields Il and 52. These filters may be of the construction as shown in our prior application above referred to, the exterior of the filter being grounded on the engine block by having it in good and firm electrical connection with the metal screen 9 I It will thus be seen that an emcient shield is provided about the spark coil, distrlbutorand variations farel prevented from passing routside the shield. by means of the filter 51, also that the generator 63 is completely radio shielded and that any disturbing variations in current are prevented from passing outside of the screen 54 by the filter 55, the exterior of which is well grounded by good electrical connection withthe engine body or crank case.

In Fig. li12 is shown a modification wherein the filter 91 is grounded on the engine block by having its exterior in good electrical connection with both the screens Il and 92.

' I It will be understood that in the foregoing the metal wires or slats employed bin the shielding devices may be of metal, as for instance'steel.

which metal may be suitably protected lfrom deterioration by galvanizing or by covering with copper or in other ways.

While the invention has been illustrated in what are considered its best applioauonsit may 20 1. A radio shield comprising at least in part afforaminous screen comprising slats crossing each other, each of said slats being of a cross section having its longitudinal dimension greater than its lateral dimension.

2. A radio shield comprising at least in port B0 a foraminous screen comprising slats crossing each other, each ofsaid slats being of a rectangular cross section and having its longitudinal dimension greater than its lateral dimension.

3. The combination with a vehicle, of propelling means therefor including an internal combustion engine comprising an ignition, and a radio shieldfor said ignition comprising a foraminous screen including crossed slats, each ofy said slats having a cross section of a dimension greater in the line of direction of movement of said vehicle than laterally thereto.

4.A radio shield comprising atleast in part a `foraminous screen comprising slats, each of said slats being of a cross section having its longitudinal dimension greaterlthan its lateral di mension. l

5. A radio shield comprising at least in part a foraminous screen comprlslng'slats. each of said slats being of a rectangular cross section having its longitudinal dimension greater than its lateral dimension.

6. The combination with ling means therefor including an internal com- Ibusion engine comprising an ignition, and a radio shield for said ignition comprising a foramincus screen including'slats. each of saidslats having a'crosssection of a dimension greater in the line of direction o!- movement o! said vehicle than laterally thereto.' '1. The combination with ling means-therefor including an. internal com- 'tionenginehavlnganignitiomofmetal cowling about said englneand a radio shield for .said

' ignition comprising a foraminous screen cooper- -sting withv said cow-ling in the formation of said rsdioshield.v 9. The combination with a vehicle. of propelsvehiclc. of propel? a vehicle. of propelbustionenginecomprlsinganignitiomsndsradio ling means therefor comprising an internal combustion engine having an ignition, of metal cowling about said engine and a radio shield for the ignition comprising a foraminous screen forwardly of said engine with relation to the direction of movement of said vehicle, and another foraminous screen-rearwardly oi.' said engine with relation to the direction of movement of said vehicle, said forami-nous screens cooperating with the said oowling in the formation of the said shield.

VV10. The combination with an internal comtion engine having ignition means, f a radio shield enclosing said engine, including said ignition means, and comprising at least in part a foraminous screen.

13. 'I'he combination with an internal combustion engine, of an ignition system therefor comprising spark plugs and a source of ignition current and a radio shield for said ignition system comprising at least in part a foraminous screen. 14. The combi-nation with an internal combustion engine having ignition means, of a radio shield for said ignition means comprising -at least in part a foraminous screen there being spaces within said screen and about pants of the engine wherein Ventilating currents for said engine may circulate.

15. The combination with an internal combustion engine having ignition means, of a radio shield for said ignition means comprising at least in part a foraminous screen there being space y between said ignition means and said screen.4

R. HARRY STONE. MELVILLE F. PETERS. 

